Role of polymer/filler interactions in the linear viscoelasticity of poly(butylene succinate)/fumed silica nanocomposite

The linear melt viscoelasticity of poly(butylene succinate) (PBS) nanocomposites containing different types of fumed silica nanoparticles (unmodified and modified fumed silica) was studied. Depending on the primary particle size and surface chemistry of fillers, distinct modes of polymer/filler interactions could be identified in the nanocomposites. The PBS nanocomposites containing silica nanoparticles with larger surface area appear to have higher density of temporary physical network structures leading to significantly increased modulus. Increasing the polymer–particle compatibility through introduction of a hydrophobic functionality on the surface of the particles resulted in strong immobilization of the PBS molecules. The presence of such improved polymer/filler interactions was confirmed by the secondary relaxation mode and rubber-like behavior, indicative of stronger adhesion between the modified SiO2 and the PBS matrix. The entangled polymer dynamic theory was used to discuss the influence of polymer/filler interactions on the relaxation behavior of PBS molecules. The relaxation hierarchy can be identified from the linear viscoelastic responses of PBS/modified fumed silica nanocomposites. Dynamic mechanical measurements showed that glass transition range was widened and the peak temperature was also shifted to higher temperature in the composites with enhanced PBS/silicainteractions.